In order to carry out foaming of a slag having a high ratio of chromium oxide having values of often above 20% of a non-corrosive melt in an AOD (Argon Oxygen Decarburization) or MRP (Metallurgical Refining Process) converter or CONARC SSt for stainless steel by adding a foam material, according to the invention a previously defined mixture (5) of a metal oxide, iron carrier, carbon and binding material in the form of pellets or briquettes (4) is introduced into the converter, which reacts in a chemically reducing manner under the slag layer (2) due to the high ambient temperature, wherein gaseous carbon monoxide formed in particular by means of the reduction process of the metal oxide with the carbon within the pellets or briquettes (4) induces the slag foaming with the gas bubbles (7) thereof and wherein the specific density of the pellets or briquettes (4) and the resolve time of the reduction process are selected so that optimal bubble formation in respect of size and duration is achieved.